Structurally characterized carboxylic acid modified zirconium alkoxides for the production of zirconium oxide thin films

A series of carboxylic acid (H-ORc) modified zirconium alkoxides (Zr(OR)4) were synthesized through the reaction of the commercially available [Zr(μ-OPri)(OPri)3(H-OPri)]2 (1, OPri = OCH(CH3)2) with a series of sterically varied H-ORc, including: formic acid (H-O2CH or H-OFc), acetic acid (H-O2CCH3 or H-OAc), isobutyric acid (H-O2CCH(CH3)2 or H-OPc), trimethyl acetic acid (H-O2C(CH3)3 or H-OBc), and t-butyl acetic acid (H-O2CCH2C(CH3)3 or H-ONc) which yielded the following products: Zr4(μ4-O)(μ-O)(μ-OFc)2(μ-OPri)4(OPri)6 (2), Zr3(μ3-O)(μ-OAc)3(OAc)2(μ-OPri)2(OPri)3 (3), [Zr2(μ-OPc)2(μ-OPri)2(OPri)4]2 (4), Zr2(μ-OBc)(μ-OPri)2(OPri)5(H-OPri) · (H-OPri) (5), Zr2(μ-ONc)(ONc)(μ-OPri)2(OPri)4(H-OPri) (6).To increase the structural variability of these precursors, we also investigated the H-ORc modifications of the novel Zr3(μ3-O)(μ3-ONep)(μ-ONep)3(ONep)6 (7) which was isolated from the reaction between Zr(NMe2)4 and 4 H-OCH2C(CH3)3 (H-ONep).The ORc-modified 7 species were isolated as: Zr3(μ3-O)(μ-OAc)3(μ-ONep)2(ONep)5 (8), Zr5(μ-O)3(μ-OPc)6(μ-ONep)2(ONep)6 (9), [Zr(μ-OPc)(μ-ONep)(ONep)2]2 (10), Zr5(μ-O)3(μ-ONc)6(μ-ONep)2(ONep)6 · (H-ONep) · 1/2(C7H8) (11). Once fully characterized, these compounds were used to generate thin films of ZrO2 to investigate the optimal structural aspects that dictate thin film density. It was determined that the majority of these compounds did not yield high quality films; however, the non-condensed species (3–5) did produce clear and continuous ZrO2 films. From this very limited set of useful precursors, the larger nuclearity species (3) led to films of higher densification.